Fix "failed to call RLocation: runfile (...)/Main: file does not exis…

…t" (#259)

Fix "bazel run gazelle" failing on Windows with the following error:
> 1:57PM FTL external/contrib_rules_jvm/java/gazelle/configure.go:139 >
could not start javaparser error="failed to start / connect to
javaparser server: failed to find javaparser in runfiles: failed to call
RLocation: runfile
contrib_rules_jvm/java/src/com/github/bazel_contrib/contrib_rules_jvm/javaparser/generators/Main:
file does not exist" (Fixes #257)

java/gazelle/private/servermanager/servermanager.go

@@ -92,11 +92,15 @@ func locateJavaparser() (string, error) {
 	}
 
 	// We want //java/src/com/github/bazel_contrib/contrib_rules_jvm/javaparser/generators:Main
-	loc, err := rf.Rlocation("contrib_rules_jvm/java/src/com/github/bazel_contrib/contrib_rules_jvm/javaparser/generators/Main")
+	javaparserPath := "contrib_rules_jvm/java/src/com/github/bazel_contrib/contrib_rules_jvm/javaparser/generators/Main"
+	loc, err := rf.Rlocation(javaparserPath)
 	if err != nil {
-		return "", fmt.Errorf("failed to call RLocation: %w", err)
+		loc, err = rf.Rlocation(javaparserPath + ".exe")
 	}
 
+	if err != nil {
+		return "", fmt.Errorf("failed to call RLocation: %w", err)
+	}
 	return loc, nil
 }